Analyzers (so-called wet assay analyzers) supply liquid reagents in bottles. These bottles, though initially closed off, are necessarily penetrated by aspirator probes when reagents are needed. Such repeated penetrations produce substantial degradation to the reagents for the following reasons: first, it has been practically impossible to reseal the bottle after the first penetration. Attempts to avoid this have used such things as penetrable septums that are supposed to reseal after penetration, but repeated penetration more or less along the same line produces "coring" which leaves a permanent air passage in the septum, air degradation of the reagent and residual deposits of the reagent on the seal which can create carry-over and growth of molds. Alternatively, penetration of the septum causes a second problem, namely deposit of septum material into the reagent liquid being stored, and this, in turn, can degrade the reagent. Although this second problem is lessened by using seals such as "duck-bill" seals, those still have the first problem, namely inadequate resealing against air contamination.
The problem then that has long faced the wet assay analyzer is how to provide on- analyzer keeping of the liquid reagents more than one or two weeks, without having to constantly replace the bottles. That is, how can a large quantity of reagent be kept on-analyzer, for one or two months, without degradation due to contact with ambient air (evaporation) or foreign materials?